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Tricky spelling drains the brain

Spelling tricky words – such as “yacht” – is no day at the beach, it seems. New brain-scan images have shown how our minds struggle when the sound of the word does not closely match its spelling.

The scans show that spelling irregular words requires more brainpower than simple ones. Specifically, areas of the brain that process word meaning show greater activity. Researchers say their findings could prompt schools to change how they teach children language.

Laura-Ann Petitto of Dartmouth College in Hanover, New Hampshire, US, and colleagues asked 12 young adults to imagine spelling a word they heard via headphones. They were then asked to judge whether the same word presented on a screen was correctly spelt.

Each participant was tested on a total of 90 words while lying in a brain-scanning machine. A third of these words had regular, phonetic spelling – such as “blink” – in which their letters corresponded directly to the sounds of the word. Another 30 words had irregular spelling, including the word “yacht”, while the remaining 30 were nonsense words, like “shelm”. “We wanted to know how words are stored in our mental dictionary,” explains Petitto.

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Spell checking

The scans revealed that more regions of subjects’ brains became active when they heard words with irregular spellings, rather than regular ones. In particular, they showed greater activity in regions such as the inferior frontal gyrus (IFG) – an area believed to store information about word meaning. Another area that showed more activity was one called the supramarginal gyrus (SMG), which helps process printed text.

By comparison, one of the few brain areas that showed slightly greater activation for regular words than irregular words was the superior temporal gyrus (STG). Petitto says this is significant because the STG is involved in auditory processing. She suggests that it plays a key role in helping people spell simple words because the sounds correspond so closely with the letters.

“This is the first evidence we have from looking at the brain about how it processes different types of words,” says Rebecca Treiman of Washington University in St Louis, Missouri, US, who was not involved in the study. She adds that spelling is still a relevant skill in the 21st century&colon; “We don’t always have our computerised spell-checkers with us.”

Resolving the debate

“This study has given us a window into the components involved in word memory,” Petitto says. She explains that neuroscientists have debated for decades whether the ability to spell relies on memorising a word as a whole, or understanding its sound components. The evidence from the scans suggests that both brain functions play an important role.

The findings may help to resolve a debate over whether children should be taught to read by memorising whole words or sounding them out, she adds. A proponent of the former method would, for example, encourage children to recognise the word “cat” at first sight, while a champion of the latter approach would have them sound out “k-ah-t”.

“This research tells us that the brain needs both phonetic segmentation as well as whole word representation” to process words, Petitto says.